1. Field of the Invention
The present invention relates to a novel curable resin comprising a polymer which contains a cyclic monomer unit and which contains a reactive group, and a resin composition comprising the same. More particularly, the present invention is concerned with a curable resin comprising a polymer which contains a cyclic monomer unit derived from a cyclic conjugated diene and which contains a reactive group in a specific amount, and a resin composition comprising the curable resin. The curable resin and resin composition of the present invention is advantageous in that both the resin and the resin composition not only have excellent durability and resistance to chemicals as well as excellent thermal and mechanical properties, but also have excellent compatibility with other resins. Therefore, the resin and the resin composition can be advantageously used as a material for use in various fields, such as automobiles, construction, civil engineering, electric and electronic appliances, fiber industry, medical equipments and other resin products.
2. Prior Art
In recent years, polymer chemistry has continuously made progress through various innovations in order to meet commercial demands which have been increasingly diversified. Especially, in the field of polymer materials to be used as commercially important materials, extensive and intensive studies have been made toward developing polymers having more excellent thermal and mechanical properties. Various proposals have been made with respect to such polymers and methods for the production thereof. Of such polymers, a curable resin having functional groups which are introduced into the resin during or after the polymerization reaction for the production of a base resin has been drawing attention. With respect to such a curable resin, the thermal and mechanical properties thereof can be improved simply by reacting the functional groups contained in the curable resin. Therefore, such a curable resin has been used in a wide variety of fields.
Conventionally, various curable resins have been developed. With respect to the above-mentioned curable resin having functional groups (wherein the resin comprises a base polymer and functional groups which are bonded to the terminals of the molecular chain of the base polymer or inserted in the molecular chain of the base polymer), the improvement of properties of the resin is achieved by reacting the functional groups contained in the resin to form a crosslinked structure. Therefore, with respect to new development of curable resins, studies have conventionally been made with respect mainly to functional groups which are to be utilized for forming a crosslinked structure by UV crosslinking reaction, electron beam crosslinking reaction, ionic crosslinking reaction, wet crosslinking reaction (curing reaction) or various chemical crosslinking reactions (such as a transesterification, a hydrazone-forming reaction, a hydrazide-forming reaction, an oxime-forming reaction and an ammonium-forming reaction). An attempt to improve curable resins by improving a base polymer per se has almost not been made. However, in accordance with the recent tendency of diversification of commercial demands for curable resins, there has been a strong demand for curable resins which are improved not only in respect of resistance to chemicals and weather resistance as well as thermal and mechanical properties, but also in respect of the compatibility with other resins, so that it has recently been desired to develop a completely novel curable resin which is much improved in respect of the above-mentioned properties and characteristics.
For example, in the field of electronic appliances for use in telecommunication, public service, industry and the like, the demand for compactness and high density attachment of parts has greatly increased. Accordingly, there has also been an increasing demand for materials which are improved with respect to thermal resistance, dimensional stability, electrical properties, flame retardancy and the like. For example, with respect to a printed circuit board, in which a copper clad laminate comprising a substrate produced from a curable functional polyphenylene ether resin has conventionally been used, a cured resin obtained from the curable polyphenylene ether resin has excellent electrical and mechanical properties; however, the cured resin is not satisfactory for use in a substrate for a printed circuit board in respect of thermal resistance and chemical resistance.
In the field of construction and civil engineering, various materials comprising a curable resin have been developed. Examples of such materials include a sealant comprising a polypropylene glycol-modified silicone curable resin (see, for example, Examined Japanese Patent Application Publication No. 61-18582), and a polymer concrete (mortar) which contains a curable resin (such as an unsaturated polyester, an epoxy resin, a vinyl ester resin, a polyurethane or a phenolic resin) as a binder for improving the toughness of a cured concrete (mortar).
However, in the field of sealants, the commercially available sealants, i.e., a polysulfide sealant, a polyurethane sealant and a silicone sealant, each have respective problems as explained below. The polysulfide sealant has disadvantages in that the sealant has a low curing rate, so that a cured sealant obtained therefrom has surface tack, and that the sealant is not satisfactory in respect of thermal resistance, weather resistance and fatigue resistance. The polyurethane sealant not only has the same disadvantages as in the polysulfide sealant, but also has a disadvantage in that it has poor adherence to glass. With respect to the silicone (i.e., organopolysiloxane) sealant, it is satisfactory in respect of the curing rate, thermal resistance, weather resistance and fatigue resistance; however, it has disadvantages in that it is difficult to coat a cured sealant obtained therefrom with a paint, and that the fungus resistance of the sealant is poor. Therefore, it has been desired to improve these sealants. For example, for solving the above-mentioned problems, Examined Japanese Patent Application Publication No. 61-18582 proposes a curable resin obtained by modifying a silicone with a high molecular weight polypropylene glycol; however, even this curable resin is not satisfactory in respect of the adherence to glass and durability, so that use of such a curable resin is inevitably limited.
In the field of the polymer concrete (mortar) also, the conventional polymer concrete has problems in resistance to chemicals, durability and mechanical properties.
Also, in industrial fields other than those mentioned above, such as paints, adhesives, printing materials, and electric and electronic parts, in which a curable resin is used, the use of the curable resin is accompanied by the above-mentioned problems. Therefore, in various fields in which a curable resin is used, it has been desired to improve the properties of the curable resin.
As one of the most practical means for solving the above-mentioned problems, it has been attempted to develop a technique of improving the structures of the main molecular chains of polymers of cyclic conjugated diene monomers (in homopolymerizing or copolymerizing not only a monomer having a relatively small steric hindrance, e.g., butadiene or isoprene, but also a monomer having a large steric hindrance, e.g., a cyclic conjugated diene monomer, and, additionally, hydrogenating the resultant conjugated diene polymer, thereby forming a cyclic olefin monomer unit in the molecular chain) so as to obtain cyclic conjugated diene polymers having excellent thermal and mechanical properties, excellent durability (such as thermal resistance and weather resistance) and excellent chemical resistance.
With respect to the homopolymerization or copolymerization of a monomer having a relatively small steric hindrance, e.g., butadiene or isoprene, catalyst systems having a polymerization activity which is satisfactory to a certain extent have been successfully developed. However, a catalyst system which exhibits a satisfactory polymerization activity in the homopolymerization or copolymerization of monomers having a large steric hindrance, e.g., a cyclic conjugated diene monomer, has not yet been developed.
That is, by conventional techniques, even homopolymerization of a cyclic conjugated diene monomer is difficult, so that a homopolymer having a desired high molecular weight cannot be obtained. Furthermore, an attempt to copolymerize a cyclic conjugated diene with a monomer other than the cyclic conjugated diene, for the purpose of obtaining a polymer having optimized thermal and mechanical properties in order to meet a wide variety of commercial needs, has been unsuccessful with the result that the products obtained are only oligomers having a low molecular weight. Further, there has been no report with respect to a polymer containing a substituted cyclic conjugated diene monomer unit and/or a substituted cyclic olefin monomer unit, wherein the monomer unit is considered to be useful for improving the properties (especially, durability, such as thermal resistance and weather resistance, and mechanical properties) of the polymer.
J. Am. Chem. Soc., 81, 448 (1959) discloses a cyclohexadiene homopolymer and a polymerization method therefor, which homopolymer is obtained by polymerizing 1,3-cyclohexadiene (a typical example of a cyclic conjugated diene monomer), using a composite catalyst comprised of titanium tetrachloride and triisobutylaluminum. However, the polymerization method disclosed in this prior art document is disadvantageous in that the use of a large amount of the catalyst is necessary, and the polymerization reaction must be conducted for a prolonged period of time, and that the obtained polymer has only an extremely low molecular weight. Therefore, the polymer obtained by the technique of this prior art document is of no industrial value. Further, this prior art document has no teaching or suggestion of a method for introducing a substituted cyclic conjugated diene monomer unit and/or a substituted cyclic olefin monomer unit into the main molecular chain of a polymer as well as modification of a polymer containing a cyclic conjugated diene monomer unit and/or a cyclic olefin monomer unit.
J. Polym. Sci., Pt. A, 2, 3277 (1964) discloses methods for producing a cyclohexadiene homopolymer, in which the polymerization of 1,3-cyclohexadiene is conducted by various polymerization methods, such as radical polymerization, cationic polymerization, anionic polymerization and coordination polymerization. In any of the methods disclosed in this prior art document, however, the polymers obtained have only an extremely low molecular weight. Therefore, the polymers obtained by the techniques of this prior art document are of no industrial value. Further, this prior art document has no teaching or suggestion of a method for introducing a substituted cyclic conjugated diene monomer unit and/or a substituted cyclic olefin monomer unit into the polymeric molecular chain of a polymer as well as modification of a polymer containing a cyclic conjugated diene monomer unit and/or a cyclic olefin monomer unit.
British Patent Application No. 1,042,625 discloses a method for producing a cyclohexadiene homopolymer, in which the polymerization of 1,3-cyclohexadiene is conducted using a large amount of an organolithium compound as a catalyst. In the polymerization method disclosed in British Patent Application No. 1,042,625, the catalyst must be used in an amount as large as 1 to 2 wt %, based on the total weight of the monomers. Therefore, this method is economically disadvantageous. Further, the polymer obtained by this method has only an extremely low molecular weight. Moreover, the method of this prior art document has disadvantages in that the polymer obtained contains a large amount of catalyst residue, which is very difficult to remove from the polymer, so that the polymer obtained by this method is of no commercial value. Furthermore, this prior art document has no teaching or suggestion of a method for introducing a substituted cyclic conjugated diene monomer unit and/or a substituted cyclic olefin monomer unit into the main molecular chain of a polymer as well as modification of a polymer containing a cyclic conjugated diene monomer unit and/or a cyclic olefin monomer unit.
J. Polym. Sci., Pt. A, 3, 1553 (1965) discloses a cyclohexadiene homopolymer, which is obtained by polymerizing 1,3-cyclohexadiene using an organolithium compound as a catalyst. In this prior art document, the polymerization reaction must be continued for a period as long as 5 weeks, however, the polymer obtained has a number average molecular weight of only 20,000 or less. Further, this prior art document has no teaching or suggestion of a method for introducing a substituted cyclic conjugated diene monomer unit and/or a substituted cyclic olefin monomer unit into the main molecular chain of a polymer as well as modification of a polymer containing a cyclic conjugated diene monomer unit and/or a cyclic olefin monomer unit.
Polym. Prepr. (Amer. Chem. Soc., Div. Polym. Chem.) 12, 402 (1971) teaches that when the polymerization of 1,3-cyclohexadiene is conducted using an organolithium compound as a catalyst, the upper limit of the number average molecular weight of the cyclohexadiene homopolymer obtained is only from 10,000 to 15,000. Further, this document teaches that the reason for such a small molecular weight resides in the fact that, concurrently with the polymerization reaction, not only does a transfer reaction occur, which is caused by the abstraction of a lithium cation present in the polymer terminal, but also a lithium hydride elimination reaction occurs. Furthermore, this prior art document has no teaching or suggestion of a method for introducing a substituted cyclic conjugated diene monomer unit and/or a substituted cyclic olefin monomer unit into the main molecular chain of a polymer as well as modification of a polymer containing a cyclic conjugated diene monomer unit and/or a cyclic olefin monomer unit.
Die Makromolekulare Chemie., 163, 13 (1973) discloses a cyclohexadiene homopolymer which is obtained by polymerizing 1,3-cyclohexadiene using a large amount of an organolithium compound as a catalyst. However, the polymer obtained in this prior art document is an oligomer having a number average molecular weight of only 6,500. Further, this prior art document has no teaching or suggestion of a method for introducing a substituted cyclic conjugated diene monomer unit and/or a substituted cyclic olefin monomer unit into the main molecular chain of a polymer as well as modification of a polymer containing a cyclic conjugated diene monomer unit and/or a cyclic olefin monomer unit.
J. Polym. Sci., Polym. Chem. Ed., 20, 901 (1982) discloses a cyclohexadiene homopolymer which is obtained by polymerizing 1,3-cyclohexadiene using an organosodium compound as a catalyst. In this prior art document, the organosodium compound used is sodium naphthalene, and a radical anion derived from the sodium naphthalene forms a dianion which functions as a polymerization initiation site. This means that although the cyclohexadiene homopolymer reported in this document has an apparent number average molecular weight of 38,700, this homopolymer is actually only a combination of two polymeric molecular chains, each having a number average molecular weight of 19,350, which chains respectively extend from the polymerization initiation site in two different directions. Further, in the polymerization method disclosed in this document, the polymerization reaction needs to be conducted at an extremely low temperature. Therefore, the technique of this prior art document is of no industrial value. Furthermore, this prior art document has no teaching or suggestion of a method for introducing a substituted cyclic conjugated diene monomer unit and/or a substituted cyclic olefin monomer unit into the main molecular chain of a polymer as well as modification of a polymer containing a cyclic conjugated diene monomer unit and/or a cyclic olefin monomer unit.
Makromol. Chem., 191, 2743 (1990) discloses a method for polymerizing 1,3-cyclohexadiene using a polystyryllithium as a polymerization initiator. In this prior art document, it is described that concurrently with the polymerization reaction, not only a transfer reaction, which is caused by the abstraction of a lithium cation present in the polymer terminal, but also a lithium hydride elimination reaction vigorously occurs. Further, it is reported that even though the polymerization is conducted using a polystyryllithium as a polymerization initiator, a styrene-cyclohexadiene block copolymer cannot be obtained at room temperature, and the product obtained is only a cyclohexadiene homopolymer having a low molecular weight. Furthermore, this prior art document has no teaching or suggestion of a method for introducing a substituted cyclic conjugated diene monomer unit and/or a substituted cyclic olefin monomer unit into the main molecular chain of a polymer as well as modification of a polymer containing a cyclic conjugated diene monomer unit and/or a cyclic olefin monomer unit.
As can be easily understood from the above, in any of the conventional techniques, it has been impossible to obtain an excellent polymer containing a cyclic conjugated diene monomer unit and/or a cyclic olefin monomer unit and having a reactive group, which can be satisfactorily used as an industrial material.
In view of the above, it has been earnestly desired to provide a novel curable resin and a resin composition comprising the curable resin, which not only have excellent durability and resistance to chemicals as well as excellent thermal and mechanical properties, but also excellent compatibility with other resins.